Giovanni di Paolo, one of the most important figures in the history of Sienese painting, was active for much of the fifteenth century. This panel is the first episode of an ambitious narrative cycle: a series of twelve scenes from the Life of Saint John the Baptist, distributed in four vertical rows of three scenes each. Although the original function and location of the cycle are unknown, it is likely that the panels formed two movable wings of a cupboard or custodia containing a sculpture or reliquary of Saint John the Baptist. The Annunciation to Zacharias, taken from the Gospel of Saint Luke (1:5-25), recounts the moment at which the Angel Gabriel foretells the birth of a son, John the Baptist, to the childless Zacharias. The incredulous Zacharias performs his priestly duties in an elaborate architectural setting whose domes and lantern recall Brunelleschi's celebrated cupola which crowns the Duomo in Florence.